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<title>FFTW 3.3.8: Installation on Unix</title>

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<a name="Installation-on-Unix"></a>
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<hr>
<a name="Installation-on-Unix-1"></a>
<h3 class="section">10.1 Installation on Unix</h3>

<p>FFTW comes with a <code>configure</code> program in the GNU style.
Installation can be as simple as:
<a name="index-configure-2"></a>
</p>
<div class="example">
<pre class="example">./configure
make
make install
</pre></div>

<p>This will build the uniprocessor complex and real transform libraries
along with the test programs.  (We recommend that you use GNU
<code>make</code> if it is available; on some systems it is called
<code>gmake</code>.)  The &ldquo;<code>make install</code>&rdquo; command installs the fftw
and rfftw libraries in standard places, and typically requires root
privileges (unless you specify a different install directory with the
<code>--prefix</code> flag to <code>configure</code>).  You can also type
&ldquo;<code>make check</code>&rdquo; to put the FFTW test programs through their paces.
If you have problems during configuration or compilation, you may want
to run &ldquo;<code>make distclean</code>&rdquo; before trying again; this ensures that
you don&rsquo;t have any stale files left over from previous compilation
attempts.
</p>
<p>The <code>configure</code> script chooses the <code>gcc</code> compiler by default,
if it is available; you can select some other compiler with:
</p><div class="example">
<pre class="example">./configure CC=&quot;<span class="roman"><i>&lt;the name of your C compiler&gt;</i></span>&quot;
</pre></div>

<p>The <code>configure</code> script knows good <code>CFLAGS</code> (C compiler flags)
<a name="index-compiler-flags"></a>
for a few systems.  If your system is not known, the <code>configure</code>
script will print out a warning.  In this case, you should re-configure
FFTW with the command
</p><div class="example">
<pre class="example">./configure CFLAGS=&quot;<span class="roman"><i>&lt;write your CFLAGS here&gt;</i></span>&quot;
</pre></div>
<p>and then compile as usual.  If you do find an optimal set of
<code>CFLAGS</code> for your system, please let us know what they are (along
with the output of <code>config.guess</code>) so that we can include them in
future releases.
</p>
<p><code>configure</code> supports all the standard flags defined by the GNU
Coding Standards; see the <code>INSTALL</code> file in FFTW or
<a href="http://www.gnu.org/prep/standards/html_node/index.html">the GNU web page</a>.
Note especially <code>--help</code> to list all flags and
<code>--enable-shared</code> to create shared, rather than static, libraries.
<code>configure</code> also accepts a few FFTW-specific flags, particularly:
</p>
<ul>
<li> <a name="index-precision-9"></a>
<code>--enable-float</code>: Produces a single-precision version of FFTW
(<code>float</code>) instead of the default double-precision (<code>double</code>).
See <a href="Precision.html#Precision">Precision</a>.

</li><li> <a name="index-precision-10"></a>
<code>--enable-long-double</code>: Produces a long-double precision version of
FFTW (<code>long double</code>) instead of the default double-precision
(<code>double</code>).  The <code>configure</code> script will halt with an error
message if <code>long double</code> is the same size as <code>double</code> on your
machine/compiler.  See <a href="Precision.html#Precision">Precision</a>.

</li><li> <a name="index-precision-11"></a>
<code>--enable-quad-precision</code>: Produces a quadruple-precision version
of FFTW using the nonstandard <code>__float128</code> type provided by
<code>gcc</code> 4.6 or later on x86, x86-64, and Itanium architectures,
instead of the default double-precision (<code>double</code>).  The
<code>configure</code> script will halt with an error message if the
compiler is not <code>gcc</code> version 4.6 or later or if <code>gcc</code>&rsquo;s
<code>libquadmath</code> library is not installed.  See <a href="Precision.html#Precision">Precision</a>.

</li><li> <a name="index-threads-3"></a>
<code>--enable-threads</code>: Enables compilation and installation of the
FFTW threads library (see <a href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW">Multi-threaded FFTW</a>), which provides a
simple interface to parallel transforms for SMP systems.  By default,
the threads routines are not compiled.

</li><li> <code>--enable-openmp</code>: Like <code>--enable-threads</code>, but using OpenMP
compiler directives in order to induce parallelism rather than
spawning its own threads directly, and installing an &lsquo;<samp>fftw3_omp</samp>&rsquo; library
rather than an &lsquo;<samp>fftw3_threads</samp>&rsquo; library (see <a href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW">Multi-threaded FFTW</a>).  You can use both <code>--enable-openmp</code> and <code>--enable-threads</code>
since they compile/install libraries with different names.  By default,
the OpenMP routines are not compiled.

</li><li> <code>--with-combined-threads</code>: By default, if <code>--enable-threads</code>
is used, the threads support is compiled into a separate library that
must be linked in addition to the main FFTW library.  This is so that
users of the serial library do not need to link the system threads
libraries.  If <code>--with-combined-threads</code> is specified, however,
then no separate threads library is created, and threads are included
in the main FFTW library.  This is mainly useful under Windows, where
no system threads library is required and inter-library dependencies
are problematic.

</li><li> <a name="index-MPI-1"></a>
<code>--enable-mpi</code>: Enables compilation and installation of the FFTW
MPI library (see <a href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI">Distributed-memory FFTW with MPI</a>), which provides
parallel transforms for distributed-memory systems with MPI.  (By
default, the MPI routines are not compiled.)  See <a href="FFTW-MPI-Installation.html#FFTW-MPI-Installation">FFTW MPI Installation</a>.

</li><li> <a name="index-Fortran_002dcallable-wrappers"></a>
<code>--disable-fortran</code>: Disables inclusion of legacy-Fortran
wrapper routines (see <a href="Calling-FFTW-from-Legacy-Fortran.html#Calling-FFTW-from-Legacy-Fortran">Calling FFTW from Legacy Fortran</a>) in the standard
FFTW libraries.  These wrapper routines increase the library size by
only a negligible amount, so they are included by default as long as
the <code>configure</code> script finds a Fortran compiler on your system.
(To specify a particular Fortran compiler <i>foo</i>, pass
<code>F77=</code><i>foo</i> to <code>configure</code>.)

</li><li> <code>--with-g77-wrappers</code>: By default, when Fortran wrappers are
included, the wrappers employ the linking conventions of the Fortran
compiler detected by the <code>configure</code> script.  If this compiler is
GNU <code>g77</code>, however, then <em>two</em> versions of the wrappers are
included: one with <code>g77</code>&rsquo;s idiosyncratic convention of appending
two underscores to identifiers, and one with the more common
convention of appending only a single underscore.  This way, the same
FFTW library will work with both <code>g77</code> and other Fortran
compilers, such as GNU <code>gfortran</code>.  However, the converse is not
true: if you configure with a different compiler, then the
<code>g77</code>-compatible wrappers are not included.  By specifying
<code>--with-g77-wrappers</code>, the <code>g77</code>-compatible wrappers are
included in addition to wrappers for whatever Fortran compiler
<code>configure</code> finds.
<a name="index-g77"></a>

</li><li> <code>--with-slow-timer</code>: Disables the use of hardware cycle counters,
and falls back on <code>gettimeofday</code> or <code>clock</code>.  This greatly
worsens performance, and should generally not be used (unless you don&rsquo;t
have a cycle counter but still really want an optimized plan regardless
of the time).  See <a href="Cycle-Counters.html#Cycle-Counters">Cycle Counters</a>.

</li><li> <code>--enable-sse</code> (single precision),
<code>--enable-sse2</code> (single, double),
<code>--enable-avx</code> (single, double),
<code>--enable-avx2</code> (single, double),
<code>--enable-avx512</code> (single, double),
<code>--enable-avx-128-fma</code>,
<code>--enable-kcvi</code> (single),
<code>--enable-altivec</code> (single),
<code>--enable-vsx</code> (single, double),
<code>--enable-neon</code> (single, double on aarch64),
<code>--enable-generic-simd128</code>,
and
<code>--enable-generic-simd256</code>:

<p>Enable various SIMD instruction sets.  You need compiler that supports
the given SIMD extensions, but FFTW will try to detect at runtime
whether the CPU supports these extensions.  That is, you can compile
with<code>--enable-avx</code> and the code will still run on a CPU without AVX
support.
</p>
<ul class="no-bullet">
<li>- These options require a compiler supporting SIMD extensions, and
compiler support is always a bit flaky: see the FFTW FAQ for a list of
compiler versions that have problems compiling FFTW.
</li><li>- Because of the large variety of ARM processors and ABIs, FFTW
does not attempt to guess the correct <code>gcc</code> flags for generating
NEON code.  In general, you will have to provide them on the command line.
This command line is known to have worked at least once:
<div class="example">
<pre class="example">./configure --with-slow-timer --host=arm-linux-gnueabi \
  --enable-single --enable-neon \
  &quot;CC=arm-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=softfp&quot;
</pre></div>
</li></ul>

</li></ul>

<a name="index-compiler-2"></a>
<p>To force <code>configure</code> to use a particular C compiler <i>foo</i>
(instead of the default, usually <code>gcc</code>), pass <code>CC=</code><i>foo</i> to the 
<code>configure</code> script; you may also need to set the flags via the variable
<code>CFLAGS</code> as described above.
<a name="index-compiler-flags-1"></a>
</p>
<hr>
<div class="header">
<p>
Next: <a href="Installation-on-non_002dUnix-systems.html#Installation-on-non_002dUnix-systems" accesskey="n" rel="next">Installation on non-Unix systems</a>, Previous: <a href="Installation-and-Customization.html#Installation-and-Customization" accesskey="p" rel="prev">Installation and Customization</a>, Up: <a href="Installation-and-Customization.html#Installation-and-Customization" accesskey="u" rel="up">Installation and Customization</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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